The lumbar spine refers to the lower back, and is where a human's spinal column curves inward toward the abdomen. The lumbar spine, which typically starts five to six inches below the shoulder blades, connects with the thoracic spine at the top and the sacral spine at the bottom. A human lumbar spine typically includes 5 vertebrae, although some individuals have six vertebrae in their lumbar spine. There are several different conditions that can affect the lumbar spine and cause pain, including disk problems. A lumbar spine fusion can be used to help alleviate pain in some individuals who are suffering from disk problems and other ailments.